This invention relates to processes for the preparation of hydroxyamines of the formula I EQU R.sup.1 --CH(OH)--CH(NHR.sup.3)--R.sup.2 (I)
wherein
R.sup.1 and R.sup.2 independently of one another are H or CH.sub.2 OH and PA1 R.sup.3 is H, C.sub.1 -C.sub.4 -alkyl or C.sub.1 -C.sub.4 -hydroxyalkyl. PA1 with an amine R.sup.3 --NH.sub.2,
Hydroxyamines of the formula I constitute valuable intermediates for the preparation of active compounds for medicaments. Thus, for example, 2-amino-1,3-propanediol (serinol) is used for the preparation of the X-ray contrast medium Iopamidol [N,N'-bis-[2-hydroxy-1-(hydroxymethyl)-ethyl]-2,4,6-triiodio-5-lactamidois ophthalamide].
A large number of processes are known for the preparation of hydroxyamines of the formula I. Thus, these compounds can be prepared by reducing corresponding nitro or oximino derivatives of amino acids or esters thereof or of oximinodicarboxylic acid esters. The reaction of formaldehyde with suitable monohydroxyamines in the presence of certain microorganisms, or the sulfation of glycerol, followed by ammonolysis, are also known. EP 0,025,083 discloses, in addition to hydrogenation processes, a method of preparation starting from epichlorohydrin, which is carcinogenic.
The processes of synthesis described have, however, a number of disadvantages. Either the yields are unsatisfactory, or the starting materials are expensive or only accessible by a complicated route, or have a very adverse effect on health, or by-products are produced for example salts which can be removed with difficulty or only with considerable effort.
A process for the preparation of 2-amino-1,3-propanediol by hydrogenating dihydroxyacetone in the presence of ammonia and a reducing agent is disclosed in German Patent 2,829,916. However, this process gives acceptable yields of about 60% of theory only on a small scale, in laboratory tests. With larger reaction batches, suitable for industrial production, the achievable yield and quality of the product fall off greatly because of appreciable formation of by-products. In addition, the catalyst employed can in most cases not be reused further owing to its activity being reduced by the by-products formed.